When liquids are to be mixed and analyzed by colorimetric or other methods or processes, mixing vessels are provided and they must be periodically drained into the analyzer or otherwise discharged. When such vessels or other vessels are drained, the typical procedure is to equip the vessels with a lowest elevation drain outlet and a valve or plug for either retaining the contents or permitting drainage of the contents.
In some cases the means for closing off the drain outlet results in leakage of fluid when closed. On the other hand, the design of the plug or valve may be such that some fluid is retained when all of the contents should be drained. When corrosive materials are to be handled or liquids which are highly reactive chemically, the choice of materials of construction of customary mechanical valves that will withstand such liquids is highly limited and such materials are also expensive.
There has been a need for an inexpensive, nonleaking drainage device for a mixing chamber or vessel, particularly such as required in an automated wet chemical analyzer which may receive any number of potentially corrosive chemical reagents. There is also a need following the addition of the reagents to the vessel for the contents to be mixed by air agitation and then drained into a suitable analyzer such as a colorimeter. There is a need also for a valve of general application or for specialized applications in the process industries. A valve without moving parts is desirable for hazardous environments, for air or inert gas injection in sterile solutions such as in the pharmaceutical industry, and use with slurries of fibrous materials wherein the usual valve seating of mechanical valves can be a problem.
Solenoid actuated mechanical valves composed of materials such as polytetrafluoroethylene have been considered but the cost of this approach has been considered prohibitive. Other designs have been proposed, such as air operated conical plug valves followed by a solenoid operated one of similar design. However, alignment problems have resulted in erratic leakage and breakage of the shafts of such valves.
Accordingly, an object of the invention is to eliminate mechanical problems and materially reduce cost and complexity of existing and proposed drainage valves and also to provide means for mixing by air agitation. Inert gases may be used instead of air when an inert gas blanket is desirable.